Having multiple systems to support different HR processes, or a mix of systems and paper-based processes, is one way to really push up the cost of HR administration and will frustrate people managers.
It also makes it far more difficult to get a consolidated view of an organisation’s employees.
There are understandable reasons why an organisation might want to deploy individual systems. Often a fully-integrated system that supports multiple processes may not offer some of the specific functionality of a best-of-breed, single-process, single-solution system.
However, organisations should seek to offset the benefits against the additional costs as part of their selection process, especially if wanting to calculate a return on their investment.
Having different systems supporting different processes creates inefficiencies and unnecessary complexity.
There is also the issue of manager adoption to consider. If an organisation asks a manager to interface with 4 or 5 different systems to manage his or her HR processes, then it's significantly reducing the likelihood that the manager will bother to use any of them.
Keeping everything in one place makes things much simpler for the user and delivers greater and wider benefits to an organisation.